Servomotor control



July 1, 1952 l.. swARTz ET AL SERVOMOTOR CONTROL.

Filed May 23, 1951 Patented July 1, 1952 SERVOMOTOR CONTROL `Louis Swartz, Philadelphia, and Minor I. Hughes, Hatboro, Pa., assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Army Application May 23, 1951, Serial No. 227,794

8 Claims.

This invention relates to a mechanical stroking control for reversible hydraulic transmissions.

It is the principal object of the invention to provide a control of the type mentioned wherein a semi-automatic mechanical control enables the pump to be stroked manually to drive a hydraulic motor in either direction.

A further object is to provide a control for hydraulic transmissions wherein the pump is automatically unstroked at a predetermined fixed neutral or zero position of the hydraulic'motor shaft when the motor has rotated to a selected one of two predetermined limiting positions.

A still further object is the provision of a servomotor system wherein a manually-operable control handle or means when moved from neutral to one limiting position in one direction effects a definite movement of the servo-motor in a corresponding direction and wherein the handle cannot again be moved to the aforesaid limiting position unless and until it is first moved from neutral in the other direction. n

Still another object is the provision of a servomotor control as in the preceding paragraph wherein the servo-motor may be run in one direction a predetermined distance lessl than maximum and then subsequently and selectively run in either direction to limiting position.

Other objects and advantages will be apparent from a study of the following specification in connection with the drawing.

In the drawing:

Fig. 1 is a diagrammatic View of the complete control.

Fig. 2 is a detail View showing the position of the pump control cam and shaft when the pump is unstroked or in neutral, no-delivery position.

Figs. 3 and 4 are detail views corresponding to Fig. 2, but showing the pump control cam and shaft in positions, respectively, for full speed in respectively opposite directions.

Referring in detail to the'disclosure, the nu-` meral identifies a pump driven by any suitable source of powersuch as a direct-connected electric motor 2'. The pump has a control slide 3 with a cam follower 4 on its end riding upon the periphery of a control cam 5 fixed to control shaft 6. A compression spring 'lA acts to continuously urge the follower 4 against the cam. The pump I may be of the Well-known rotary, reversible delivery, variable displacement type in which the direction and amount of displacement from a neutral or no-delivery position, of a slide block connected with shaft 1. Since such pumps frequently have afspring incorporated in the pump itself which urges the slide block in one direction of motion, spring l may be omitted when such a pump is used, or the spring 'l may be supplementary to the one incorporated in the pump and act in the same direction.

The discharge and intake pipes B and 9 lead from pump l to a reversible hydraulic motor I0 having its rotor connected to drive shaft I I having gears |2 and I3 fixed thereto. For the purpose of definite description, the connections and arrangements are assumed to be, and may be, such that when control rod 1 is moved to the left, as viewed in Fig. 1, that is, when cam 5 and shaft B are rotated counterclockwise from the neutral or no-discharge position shown, the discharge from the pump is such as to cause motor l0 to rotate clockwise as viewed. The corresponding position of the cam and control shaft for maximum discharge is shown upon Fig. 4. Conversely, when the cam 5 and shaft B are rotated clockwise to the position shown upon Fig. 3, the control rod 6 is moved outwardly or to the right to its maximum position, the direction of delivery of the pump is reversed, and motor I0, is rotated counterclockwise. Rotation of control cam 5 is effected by a lever I4 fixed to a shaft I5. Gears I6 and |'l connect shafts 6 andY l5 for simultaneous rotation.

Shaft E has a gear I8 and a cam I9 fixed thereto. Pinion I8 meshes with a rack 20. A. first stop shaft 2| has a swivel connection at 22 with rack 20 whereby the shaft may rotate relatively to the rack, but is constrained to move as a unit with the rack in axial translation. Shaft 2| has an elongated gear 23 fixed thereto as well as a pair of stops 24 and 25 axially spaced therealong. The construction, purpose and operation of these stops will be subsequently described.

Cam I9 has a relatively abrupt riser portion |9a. The periphery of the cam is engaged by a slide 2S under the urge of a compression spring 21. Slide 26 carries a cam portion 26a engaged by one end of a rack 2 8 at right angles to the slide and parallel with shaft 6. Rack 28 meshes with, and drives, pinion 23 for all axial positions of shaft 2| and is urged upwardly into continuous Contact with cam portion 26a, by a compression spring 29.

Gear I3 meshes with and drives a gear 30 fixed to a shaft 3| which has another gear 32 xedlto its other end. Gear 32 mesheswth and translates a rack 33 in a direction parallel with shaft 2 I.

and adjacent stop shaft 2|. A pair of stops 35 This rack has an operating shaft 34 fixed to and extending from one end thereof parallelto.

cam I9 has moved slide 26 tov maximum position to the right, the resulting movement of rack 23 and rotation of gear 23 and shaft 2l also rotates stop 25 to a position wherein it will be engaged by stop when the latter is axially translatedfinV the manner previously described.

In the neutral position of the parts as shown', wherein manually operable handle I4 is at-the neutral or 0 position, operation of the handle Movement -of handle I4 clockwise to position III effects a corresponding and proportional movement of shaft 2| and stop 24 to the left. It also rotates cam 5 to force pump control shaft 'I inwardly and causes pump I to discharge in a direction rotating motor I and driven element I2 clockwise. Since the rotation of shaft E is counterclockwise, slide 26 continues to; ride upon the base circle of cam I9 and no rotation of shaft 2:I and its stops is effected. Clockwise rotation of motor I0 moves stop 35 to the right and causes it toengage-stop 24, thus translating shaft 2I to the fright, restoring handle I4 and the pump control shaft 'I1 toneutral positions and stopping further movement witlrv all parts Ias shown on Fig. 1.

The handleimay now' be again moved to either of positionsT or 11.

to position III is impossible because the` slide block of the pump is in neutral, motor l0 is at rest and rack 3?Y and stops 35- and 3B are-motion.-

less. Since stop 24 is at th-is time in contact with` stop 35', furthermovement of stop 24 to the left is impossible and handlev I4 is thus prevented from movement. to position IIL Under such conditionsv handle I4 can be moved only in the counterclockwise direction to position I or 11. Assuming movement Vthereof to position I formaxmum rotation of gear I2r counterclockwise, gear I8 is turned and shifts rack 2U, shaft 2'I` and itsstops 24 and 25 to the right. At the same time, cam IS!Y is rotated until its riser or nose ISa passes acrossand to the other side of slide. 26;r The action causes a. momentary depression of rack 28 and a corresponding rotation,

of shaft 2l and its stops 24 andA 25, The parts are so proportioned and relatedthat, after handle I4 has been fully turned to position 1, slide 26 again rides upon the base circle of cam I8, with portion I9a at the other sider of the slide 26 from that shown in Fig. 1. Thus shaft 2| is given a momentary rotation during movement of handle I4 to position I andV then returned by spring 29 to itsY original or neutral position. The parts are so arranged that stop 25 is translated to the right past stop 36 without interference therefrom, so that, when shaft 2l is returned to its neutral rotational position, stop 36 can be shifted without obstruction from stop'25.Vv Thus the movement of handle I 4 to position I shifts stop 24 to the' right a xed distance for engagement by stop 36 when the latter is moved to the left. As shaft 6` is thus rotated clockwise, cam 5` is correspondingly rotated to effect movement of shaft I of the pump control to the position shown upon Fig. 3. This action causes the pump to discharge in a direction rotating motor IIIV counterclockwise, whereby rack 33, shaft 34'and stops 35 and 36y are shifted to the left. Stop 36 then engages stop 24 and moves shaft 2 I, gear 23 and rack 20' to the left until the parts-are restored to the initial or neutral position shown wherein the pump is restored to rio-discharge position, motor Ill ceases rotation and handle I4 is restored to the"0 or neutral position. The action is such that motor I0, and driven element I2 are rotated a predetermined nxed number of rotations counterclockwise.

Since stop 36 is now in engagement with stop 24, the handle I4 cannot be turned to the I or II positions without rst being turned to the III position. That is, before itv canbe again rotated. counterclockwise, it must be rotated clockwise.

Movement of handle I4 to position II effects anangular movement of cam I9 such that riser lila rests in contact withthe end of slide 26, rack 2t.A is held-:indepressed position, andshaft 2I and stop 25V are rotated tofapositionwherein stop 25 will bev engaged. by stop. 36A whenV the latter is axially translated. with. rack v3th Also stop-25 is shifted to theright awfixedfv distance and cam 5 effects an outward movement of pump-control shaft 'I to drive motor lcounterclockwise. As a result Vstop 3S isshifted tothe left into engagement-with stopl; whereby shaft 6 is rotated to restore eam- 5. and handle I4 to-neutral position and to restore cam` I9 to the position shown in Fig. 1. The construction and relation of the parts are such that stop 25vv 'is` rotated outvr of contact with stop 36 at the instant the-pumpisresto-red to neutral or Ilo-discharge position and control handles I 4 restored to 0 position.

FromV thispositionit is possible torun the gear or driven element I2 the maximum number of rotations counterclockwise :by movinglever I4 either` to position I or to position IL Since the movement of handle orlever I4.to either the I or II positions merely moves stop-24to the right a distance yvarying with thefposition selected, but always to the left of stop-36, the operation of motor III ceases WhenstOp 36 under movement of the motor,4 has engaged and restored stop-24 and shaft 2IY- to theA neutral or no-delivery position. Hence, nof matter Whether handle I4 is shifted tti-position I or position IL as identified on Fig. 1, motor Ill always comes; to rest at the same maximum number of revolutions from zero or neutral pOsition. Also from the final position mentioned in the preceding paragraph, handle I4 can be shifted to position III to thereby effect clockwise rotation of motor I0 to its maximum position.

In theclaims, the term neutral or neutral position as appliedto mechanism including control.- handle I4 means a position thereof wherein motor IllA is at rest. The term positive as applied to the driving connections means a connection inwhich the driving movement isv at all times directly proportional tothe resulting driven movement.

Having now fully disclosed Ythe invention what I claim anddesiretoY secure by Letters Patent is:

l. In :a servo-motor system, a reversible servomotor, control means manually operable between first and second limiting positions to effect operation of said servo-motor in respective opposite directions of rotation, first-.and second stopsV in xed relation, means responsive to operation of said servo-motor shiftingsaid stops as a unit, a thirdk stoppositioned between said rst and second stops and engageable thereby, and a driving connection between said third stop and said control means.

2. In combination, a reversible servo-motor, power means driving said servo-motor, control means for said power means and manually operable between rst and second limiting positions, through neutral, movement of said control means to said limiting positions effecting movement of said servo-motor in respectively opposite directions and in neutral effecting stoppage of said servo-motor, rst and second spaced stops, a driving connection between said motor and stops moving the latter as a unit, a third stop positioned between and engageable by each of said first and second stops for a corresponding direction of movement of said motor, and a positive driving connection between said control means and said third stop.

3. In a servo-motor system, a reversible hydraulic servo-motor, a reversible delivery hydraulic pump, connections between said motor and pump to drive said servo-motor from said pump in a direction corresponding to the direction of delivery of said pump, manual control means movable between pre-determined limiting positions and operable to effect the discharge of said pump from maximum in one direction,

through neutral, to maximum in the other direction to thereby control the direction of rotation of said motor, a control stop, means positively moving said stop between predetermined limits in response to operation of said control means, a pair of spaced stops movable in fixed relation, and a positive driving connection between said servo-motor and said spaced stops moving the latter as a unit, whereby to return said control means and pump to neutral position in response to a predetermined corresponding movement of said servo-motor.

4. In a servo-motor system, a reversible hydraulic servo-motor, a reversible-delivery hydraulic pump, connections driving said servomotor from said pump in a direction corresponding to the direction of discharge of said pump, control means movable to vary the discharge of 'said pump from maximum in one direction,

through neutral, to maximum in the other direction, when said control means is moved between rst and second limiting positions, respectively, rst and second spaced stops, a connection between said servo-motor and stops moving the same as a unit in a first fixed path, a third stop movable between said first and second stops in a second path parallel to said iirst path for selective engagement and movement by said first and second stops, and a positive driving connection between said control means and said third stop whereby said third stop is moved to return said control means and pump to neutral in response to movement of said control means to either of said limiting positions whereby to effect a predetermined movement in a corresponding direction, of said servo-motor.

5. In a servo-motor, a reversible servo-motor, control means operable between first and second fixed limiting positions, through neutral, to effect movement of said servo-motor in corresponding directions, first and second spaced stops movable in a rst direction as a unit in fixed relation, a first positive driving connection between said servo-motor and said stops, a third stop between said rst and second stops for engagement and movement by said first and second stops for a corresponding direction of movement of said servo-motor, a second positive driving connection between said third stop and control means, moving the same in said first direction, a fourth stop movable as a unit with said third stop in said first direction and movable relatively to said third stop in a second direction from a first position out of the path `of said first and second stops to a second position for engagement by one of said first and second stops, and means responsive only to predetermined movement of said control means from neutral to a predetermined position short of one said limiting position to effect movement of said fourth 'stop to its said second position. i

`6. A servo-motor system comprising, a reversible hydraulic servo-motor, a reversible-delivery pump, iiuid pressure connections between said servo-motor and pump, control means for said pump, said control means being operable between iirst and second limiting positions, through neutral, to eii'ect reversal of delivery of said. pump and a corresponding direction of movement of said servo-motor, first and second spaced stops, a positive, irreversible driving connection between said servo-motor and first and second stops, moving said stops as a unit, a third stop movable between and selectively engageable by said first and second stops, a positive driving connection between said third stop and control means, said driving connections being constructed and arranged to restore said control means to neutral by engagement between said first or second stops, with said third stop, whereby a predetermined movement of said servo-motor in a selected direction restores said control means to neutral and stops said servo-motor, a fourth stop movable in a first direction as a unit with said third stop and movable in a second direction relatively to said third stop from a rst position out of the path of said rst and second stops to a second position in said path, and means responsive only to movement of said control means from neutral to a predetermined position short of one said limiting positions, to move said fourth stop into its said second position.

7. In a servo-motor system, a reversible hydraulic servo-motor, a variable delivery pump, a control element for said pump movable from a rst limiting position effecting maximum discharge of said pump in one direction, through neutral to a second limiting position effecting maximum discharge of said pump in the other direction, connections between said pump and servo-motor driving the latter in opposite directions for respective directions of discharge of said pump, a cam shaft, a cam on said shaft :in operating engagement with said control element, a handle manually operable between limiting positions, operative connections between said handle and cam shaft to effect operation of said control element and pump to corresponding limiting positions, an operating shaft, rst and second spaced stops fixed to said operating shaft, a positive driving connection between said servo-motor and operating shaft axially translating the latter in response to operation of said motor, a control shaft parallel and axially translatable adjacent said operating shaft, a third stop on said control shaft between and selectively engageable with said rst and second stops, and a positive driving connection whereby said cam shaft and control shaft are respectively rotated and translated in unison.

8. In a servo-motor system, a reversible hydraulic servo-motor, a reversible-delivery pump, a control element for said pump movable between 7 n first andsecond limiting positions, fsaid positions corresponding -to :maximum discharge of -said pump vthrough neutral in opposite directions, respectively, connections between said pump and servo-motor driving the vlatter in opposite directions for respective directionsof discharge of said pump, a camshaft, a cam fxedon said shaft and in operating engagement with said control element, a handle'operable between limiting positions, a driving connection between said handle and camshaft to effect operation of said control element between limiting positions for corresponding limiting positions of said handle, an-operating shaft, first and second longitudinallyspaced stops on said operating shaft, a positive driving connection between said servo-motor and operating-shaft longitudinally translating the latte-r inresponse tooperation of said motor, a control shaft mounted Afor rotation and longitudinal translation, a driving connection whereby said cam shaft rotates in timed relationwith longitudinal translation of said control shaft, a third stop on said control shaft between and selectively engageable withsaid first and secondV stops for all positions of rotation of said control shaft, a fourth stop on said control shaft and engageable with one/of said -first and second stops for a predetermined -rotational position of said control shaft only, and means responsive to movement of said handle to -a position short of one said limiting position to rotate said control shaft into said predetermined rotational position.

LOUIS SWARTZ.

MINOR I. HUGHES.

No references cited. 

